Saturday, May 25, 2013

Every once in awhile someone asks a question that causes me to do a fact check and research that leads to a different answer than I would have given otherwise. In this case, the question was: "Can anyone tell me why these A3D-1Q's had open bomb bay doors...if they were
originally (sealed) to accommodate the ECM* monitors in an unpressurized bomb bay compartment. It would seem that opening the bomb bay
would be impossible if it was converted to an ECM* compartment"

Five Douglas A3D-1s bombers were converted to have an electronic reconnaissance mission capability by the Navy, reportedly at the Navy repair and overhaul facility at Norfolk, Virginia, and redesignated A3D-1Q. The A3D-1Q Characteristics Summary (CS) dated 15 July 1957 gives the Bureau Numbers (130356 and 130360-3) and states that it had a crew of seven and a "pressurized cabin". Other published sources state that the bomb bay was not pressurized (the bombs didn't need it) even though there were guys sitting back there or that there was a pressurized "capsule" installed in the bomb bay.

The bomb bay door that's open is the one on the left. The right one was modified to add a canoe-like fairing to house antenna(s); it could be opened if required. There were also mission-specific antennas located in the fairings on the side of the forward fuselage and the tip of the tail.

Two of the A3D-1Qs were delivered to VQ-1 and two to VQ-2 in late 1956. (Chuck Huber reports that at least one A3D-1Q was delivered to VQ-1 still glossy Sea Blue.)

Capt East makes it clear that these were four-place, not seven-place, airplanes: pilot, navigator, crew chief (who would also have been the tail gunner), and a radio-electronics operator. There were a couple of other indicators as well as to the number of crewmen. In both fatal crashes, one at VQ-1 and one at VQ-2, there were only four crewmen aboard; although one was a proficiency flight, the other was almost certainly operational. There are only four guys in this picture of a VQ-1 A3D-1Q crew.

At first I assumed that the fourth crewman was located in the bomb bay but the more I thought about it, the less sense this made. The bomb bay was not pressurized (although the flight deck wasn't pressurized much and pressurization isn't absolutely necessary for flight at high altitude). There didn't appear to be any side or upper escape hatches added to the mid fuselage, much less a porthole. Theoretically, however, bailout could be accomplished by opening the bomb bay door and the fourth crewman would probably ride the jump seat on the flight deck for takeoffs, landings, and when a ditching or crash landing was going to occur.

Closer inspection of the forward fuselage revealed two interesting features though. First, the periscope fairing had been removed consistent with the removal of the ASB-1 bombing system since the electronic reconnaissance mission didn't require it. Second, the aft part of the canopy appeared to have be replaced with solid panels and the sides of the canopy looked nonstandard as well.

As a result, I suspected that the flight deck of the A3D-1Q was configured with a fourth work station. Eliminating the bombing system would allow the right front seat to be moved forward, creating adequate space behind it to accommodate it.

Captain East confirmed by email that the A3D-1Q had a four-man crew and they were all seated on the flight deck. The fourth crewman's work station was not in the bomb bay.

This is a comparison of a poor-quality A3D-1Q canopy photo with one of an A3D Bomber that suggests the seating arrangement on the right in the A3D-1Q was the same as existing one on the left although the fourth seat reportedly faced forward.

However, one second-hand report has the aft right-hand seat facing forward, with the back of the seat consisting of "the aft bulkhead of the cockpit". That would be consistent with the addition of a jump seat during A3D-2 production.

It is also described as a bucket seat, which would seem to be more appropriate for crew comfort on a long mission.

How to explain the 1957 CS that lists it as a seven-place airplane with a pressurized cabin? This is almost certainly an error, possibly caused by confusion with the forthcoming A3D-2Q (the mockup had been reviewed in September 1954) that was a seven-place airplane with four crewmen added in a rearrangement of the fuselage interior that created a pressurized cabin immediately behind the flight deck. (See http://tailspintopics.blogspot.com/2010/09/mighty-skywarrior.html) The same applies to the published and online instances of the A3D-1Q described as having seven crewmen.

There might be enough hardware left in it to ascertain the configuration of the fourth crew station. It was however, used by Westinghouse to test side-looking radar, among other things, so the flight deck might have been rearranged at some point and no longer represents that of the A3D-1Q.

I'm also hopeful that a connection gets made with an A3D-1Q crewman who has a reliable memory...

Tuesday, May 14, 2013

It might not even be the tenth one. For sure there were a few F6F drones catapulted during the Korean War on combat missions:

There were F6F Hellcats launched as target drones.

At least one, anyway:

National Naval Aviation Museum via Rick Morgan

And then there was at least one Regulus missile launch using a cart:

And there may have been some TDN or TDR drone catapult launches although all I've ever seen are deck-run takeoffs of the TDN:

Since the Brits were first with just about everything concerning carrier-based operations, I wouldn't be surprised if they had held the honour on this achievement as well.

But congratulations to Northrop Grumman and the Navy nevertheless. The launch itself is actually not a big deal; F-18 pilots aren't even supposed to have their hand on the control stick during the launch. The taxi forward and hookup to the catapult unmanned? That is a much bigger deal and the X-47B is the first to do that.

Once again, I've come across something that I would have liked to include in one of my books, in this case the crash report for XF7U-1 BuNo 122472 on 28 September 1949 during takeoff at Vought's temporary flight test facility at Ardmore, Oklahoma.

I had assumed that the crash was caused by the load asymmetry (there was a drop tank loaded on the right inboard wing) combined with a new yaw control concept and that it was the first flight in this configuration. I speculated on how that caused the crash. That took some doing because you'd expect a load on the right wing to result in the right wing tip hitting the runway, not the left, if there wasn't enough control power at takeoff speed to keep the heavy wing up.

As it turns out, however, the load was on the right wing and was even greater than in the reports I relied on, a 250-gallon drop tank not 150. Not only that, this was Thayer's third flight that day in this configuration, which was a big surprise. The only difference on the takeoff this time was a gusty crosswind from the right, not down the runway as before, and he had the canopy open instead of closed. As with the previous two takeoffs, the leading edge slats were closed, which was the preferred configuration for field takeoffs at the time.

Thayer lifted off holding left rudder as I had assumed because of the drag and weight of the drop tank on the right side. (It was even more necessary with a crosswind from the right that I didn't know about.) He then moved the gear handle to the up position, so the gear doors opened and the landing gear began to retract. As the landing gear was coming up, the airplane began to slowly yaw to the left. Thayer pushed right rudder but the left yaw didn't stop and the left wing began to drop. Right stick and more right rudder didn't stop the left roll and yaw so he pulled the throttles off, not wanting to keep trying to fly an airplane that he was not in control of.

The left wingtip touched first just off the left side of the runway, with the airplane slewing around to the left about 100 degrees as it slid across the grass, wheels up, for about 750 feet. During the slide, the forward fuselage broke off just ahead of the engine inlets and wound up lying on its right side at right angles to the fuselage ahead of the left wing.

Vought couldn't find anything wrong with the control system, engines, or anything else for that matter. Although the XF7U was instrumented, it was by means of a photo-observer panel, which means that a picture was taken of a separate set of instruments every five seconds. In other words, the engineers were looking at relatively infrequent snapshots of a rapidly deteriorating situation. Their best guess was that Thayer was too slow and not aggressive enough in his initial response to the left yaw that he had caused with the left rudder required on the takeoff roll. It didn't help that while the landing gear was coming up, there was a significant reduction in directional stability. Or that the wind was gusty.

Their conclusion: "The airplane would be expected to yaw and roll to the left when stalled at high powers with slats closed. The accident, therefore, is explainable on the basis of an early onset of a stall."

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In 1956, at age 12, I lived on NAS Sangley Point in the Philippine Islands. Always enamored with airplanes, I imprinted on the Cougars, Banshees, and Skyraiders then being deployed. Not able to be a Naval Aviator because I was nearsighted, I instead became an aeronautical engineer and general aviation pilot. Now retired, I write books and monographs on U.S. Navy aircraft.